Anchor plate means for reinforcing rods

ABSTRACT

Use of pretensioned elongated reinforcing rods in concrete structures, the rods being terminated at various intermediate ends of the structure, and special anchor arrangements for permitting intermediate termination of the rods.

United States Patent 1191 1111 3,841,599 Van Buren 1 Oct. 15, 1974ANCHOR PLATE MEANS FOR [56] References Cited REINFORCING RODS UNITEDSTATES PATENTS [75] Inventor: Myers Van Buren, Cheriton, Va. 2,638,1845/1953 Sturdivunt .1 254/190 R Assigneez Bayshore Concrete Pmducs p2.695,!54 11/1954 Karig 264/228 Cape Charles, Va. FOREIGN PATENTS ORAPPLICATIONS 22 Fikd: May 9 1973 561,472 4/1957 Italy .1 264/228 PP N05358,470 Primary ExaminerRobert D. Baldwin Relaed Application DataAssistant Examiner-John McQuade [62] Division of $81. No. 151,284, June9, 19712111340, l' Agent Calla Harper 3,738.786, which is a division ofSer. No. 8,139,1an. Sumo 16, 1970, Pat. No. 3,652,756, which is adivision of Ser. N0. 639,371. May is. 1967. Pat, No. 3,501,881. [57]ABSTRACT Use of pretensioned elongated reinforcing rods in con- [52]U581. "6424??? Crete structures the rods being terminated at Various g dintermediate ends of the structure, and special anchor arrangements forpermitting intermediate termination of the rods.

7 Claims, 11 Drawing Figures sum 1 BF 2 PATENIEB BUT I 5 [974PATENTEUUBT 1 51814 3.841.599 saw a or a ANCHOR PLATE MEANS FORREINFORCING RODS This is a division, of U.S. Pat. application Ser. No.151,284, filed June 9, 1971 for Reinforcement of Concrete Structures nowU.S. Pat. No. 3,738,786 which, in turn, is a division of U.S. Pat.application Ser. No. 8,139 filed Jan 16, 1970 for Reinforcement ofConcrete Structures now U.S. Pat. No. 3,652,756 which, in turn, is adivision of U.S. Pat. application No. 639,371, filed May 18, 1967 forReinforcement of Concrete Structures, now U.S. Pat. No. 3,501,881.

This invention relates to the reinforcing of concrete, and moreparticularly it concerns the impartation of predetermined stresses atdifferent locations along concrete structures.

The present invention is particularly useful in connection with themanufacture of concrete poles and columns for supporting high tensionwires and the like. These poles and columns, in addition to their basicvertical supporting function, must also be capable of withstandinglateral bending loads imposed by he wires or cables which they support.Such bending loads however, impose tensile stresses on the concrete, andunless adequate provision is made for reinforcing, the concrete willfail. in general, such reinforcing is provided by means of elongatedsteel tension members embedded in the concrete and placed under apredetermined degree of tension. This imposes a compressive stress onthe concrete which it easily withstands; and at the same time it servesto absorb nearly all its tensile stresses produced under lateral orbending loads.

Because of the high weight to strength ratio of concrete, it isdesirable to taper elongated vertical support members made of concrete.This permits of a more efficient structure, since each cross sectionalarea may be tailored to the total weight being supported by it. As aresult a uniform unit stress may be maintained throughout the structure.

The tapering of an elongated concrete structure however, presentscertain problems with regard to the provision of reinforcement. This isbecause the elongated reinforcing rods which are embedded within theconcrete are each subjected to a constant tensile stress throughout itslength. Thus the total compressive force imposed by the reinforcing rodsupon the concrete is the same at each cross sectional location along thestructure. This uniform compressive force however is imposed upondifferent cross sectional areas; and toward the tip of the structure,where the cross sectional area is smallest, the unit compressivestresses become quite high in relation to those near the base of thestructure.

Prior attempts to solve this problem and to obtain a more uniform unitstress throughout a tapered concrete structure have been unsatisfactory.According to one technique, the reinforcing members were selectivelycoated in various regions along their length to prevent their bonding tothe concrete. Thus those reinforcing members which were not bonded inthe chosen regions would not impose compressive stresses in theseregions. This technique required an excessive amount of reinforcingmaterial for the amount of useful reinforcing produced. Moreover, inthose regions where the reinforcing material was not bonded to theconcrete and was left unstressed, the concrete was actually in aweakened condition due to the presence of the internal passages throughwhich the reinforcing material extended.

According to another prior technique, only a sufficient amount ofprestressed reinforcing material is used to produce a desired amount ofunit stress at the small end of the concrete structure. Then additionalunstressed reinforcing is added to the larger end of the structure inorder to strengthen it in that region. While this avoids the small endweakening problem of the first technique, it also requires uneconomicaluse of reinforcing material.

The present invention overcomes. all of the above described problems ofthe prior art. The present invention makes possible the provision of areinforced tapered concrete structure subjected to a substantiallyuniform compressive unit stress throughout its length. No problems ofweakening are presented with the arrangements of the present invention;and maximum efficiency is obtained in the use of reinforcing material.

Essentially, the present invention makes use of various reinforcingmembers which are prestressed in tension and which are embedded within acontinuous integral concrete structure. These reinforcing members areterminated at different locations within the concrete structure so thatthe unit stress at any cross section can be established by providing atsuch cross section a proper number of properly stressed reinforcingmembers.

According to a particular feature of the present invention anoveltechnique is provided for manufacturing concrete structures havingvarious prestressed reinforcing members embedded at different locationstherealong. According to the technique a concrete forming mold isprepared for forming the reinforced structure. Anchor members aremounted on the sides of the mold and extend inwardly a distance from theinner mold surface. Cables or other elongated reinforcing members areconnected to the anchor members and are subjected to a predeterminedtensile stress. Thereafter the concrete is poured into the mold andallowed to set. Upon completion of this set, the cables are disconnectedfrom the anchor members, as by burning them off. The anchor members arethen removed along with the mold andthe voids left in the concretestructure'by the anchor members are filled up with additional concrete.

According to a further feature of the invention there are provided novelanchor member arrangements involving anchor members which may besecurely mounted to the sides of the mold for holding reinforcingmembers inside the mold under a high degree of tension, and which at thesame time are capable of easy removal from the hardened concretestructure. These novel arrangements comprise special plates of generallytriangular or quarter-round configuration which extend through a slot inthe mold side and which are pinned in place to lugs or flanges formedadjacent the slot on the outer mold surface. The cable or otherreinforcing member to be embedded in the finished structure is securedto the plate in such a manner that the plate holds the reinforcingmember inside the mold while withstanding the tensile forces imposed onthe reinforcing member. The securing arrangement however involves only alooping or abutment type interconnection between the plate and thereinforcing member so that the plate may easily be withdrawn out throughthe slot after the concrete has set while leaving the cable embedded inthe concrete.

There has thus been outlined rather broadly the more important featureof the invention in order that the detailed description thereof thatfollows may be better understood, and in order that the presentcontribution to the art may be better appreciated. There are, of course,additional features of the invention that will be described hereinafterand which will form the subject of the claims appended hereto. Thoseskilled in the art will appreciate that the conception upon which thisdisclosure is based may readily be utilized as a basis for the designingof other structures for carrying out the several purposes of theinvention. It is important, therefore, that the claims be regarded asincluding such equivalent construction as do not depart from the spiritand scope of the invention.

Specific embodiments of the invention have been chosen for purposes ofillustration and description, and are shown in the accompanyingdrawings, forming a part of the specification wherein:

FIG. 1 is a perspective view of a tapered hollow concrete supportingpole made according to the present invention;

FIG. 2 is a section view taken along line 22 of FIG.

FIG. 3 is a section view taken along line 3-3 of FIG. 1;

FIG. 4 is a section view taken in side elevation of a mold arrangementfor centrifugally casting the pole of FIG. 1;

FIG. 5 is a section view taken along lines 5-5 of FIG.

FIG. 6 is a fragmentary section view taken along lines 6-6 of FIG. 4;

FIG. 7 is a fragmentary section view taken along lines 7- 7 of FIG. 1;

FIG. 8 is a fragmentary section view illustrating a modified reinforcingrod anchor arrangement according to the present invention;

FIG. 9 is a section view taken along line 9-9 of FIG. 8;

FIG. 10 is a view similar to FIG. 8 but showing a still furthermodification of the reinforcing rod anchor arrangement according to thepresent invention; and

FIG. 11 is a section view taken along line 11-11 of FIG. 10.

FIG. I shows a centrifugally cast tapered concrete supporting pole ofcircular cross section and formed with a hollow circular core 22. Asshown in dotted outline, a plurality of elongated steel reinforcing rodsor cables 24 are embedded within the concrete of the pole 20 and extendalong its length. These reinforcing rods are prestressed; that is, theyare subjected to a predetermined amount of tensile stress by externalmeans during the time that the concrete which forms the pole 20 ishardening. Subsequent to hardening of the concrete, the rods 24 arereleased. As a consequence of this, these rods serve to inducecompressive stresses along the length of the pole 20 thus increasing theability of the pole to withstand tensile strains which are produced byforces tending to deflect or bend the pole in a lateral direction.

As stated above, the pole 20 is tapered from end to end. The purpose forthis is to compensate for the high weight to strength ratio of theconcrete, and to provide for a uniform unit supporting stress at eachcross sectional location along its length. In this connection it will benoted that the loading at any location along the pole is made up of boththe load being supported by the pole and the weight of the pole concreteabove the location. Thus the total loading increases toward the'bottomof the pole. This increase in total loading is compensated for byincreasing the pole cross-section toward the bottom thereof, thusproviding for a uniform compressive stress throughout its length.

In addition to the pole loading caused by the load it supports and theweight of the pole itself, the pole 20 is also subjected to loadingequal to the sum of the ten sile forces in the reinforcing rods 24.These rods, by virtue of their tensile stresses, produce an equal amountof compressive loading on the concrete. Now this reinforcing rod loadingis continuous along the length of the rods. Consequently the variationin the pole cross section results in a variation in unit stress producedby the rods 24 at different cross-sectional locations along the pole.

According to the present invention, this is compen sated for byproviding a greater number of the reinforcing rods 24 where thecross-sectional area of the pole 20 is largest and a lesser number ofcables where the cross-sectional area of the pole is smallest. Each ofthe cables is subjected to a continuous tensile stress along its length.However, certain of the cables are terminated intermediate the overalllength of the pole 20. Thus, as can be seen in FIG. 1 the base sectionof the pole, illustrated by the distance A, isprovided with the greatestnumber of reinforcing rods 24. A first portion of these rods however,(i.e., rods 24) are terminated at the upper end of the base section A.The remainder of the rods 24 continue up the length of the pole 20through an intermediate section B. At the upper end of this section, asecond portion (i.e., rods 24") are terminated. The remainder of therods 24 then continue on through an upper portion C of the pole 20 andterminate at its upper end. Thus, as shown at the lower end of the pole20 in FIG. 1 there are provided a maximum number of reinforcing rods 24which generate a greater total compressive force upon the concrete inthe lower section A of the pole. This greater force is counteracted bythe greater cross-sectional area in this region of the pole so that theunit'stress is not exorbitantly high. Thereafter, as illustrated in FIG.2, a smaller number of the reinforcing rods 24 extend through theintermediate section B. Each of these rods is subject to the sametensile stress that it experiences in the lower section A. However, thelesser number of these rods in the intermediate section B results in asmaller total compressive force exerted in this region of the pole 20.On the other hand, the total cross-sectional area of the pole 20 in theintermediate section B is less than it was in the lower section A sothat the total unit stress produced by the reinforcing rods on theconcrete in the intermediate region is approximately that produced inthe lower section A.

Similarly as shown in FIG. 3 an even smaller number of the reinforcingrods 24 pass through the upper region C. Again, these rods are eachsubjected to the same tensile stress which they experienced in passingthrough the lower and intermediate sections A and B of the pole 20.Thus, the total compressive force exerted by them on the concrete in theupper section C is less than that exerted by the reinforcing rods in thelower and intermediate sections A and B. However, this compressive forceis resisted in the upper section C by an even smaller concrete crosssection. Therefore the unit stress in the upper section C againapproximates that existing in the lower and intermediate sections A andB.

It will be noted that although the various groups 24' and 24" of therods 24 terminate at locations intermediate the ends of the pole 20, thepole itself is of continuous integral construction and is formed as aunit at one time.

A centrifugal casting arrangement used to produce the pole 20 is shownin FIG. 4. This casting arrangement comprises a tapered cylindricalsteel outer shell 26 having collars 28 and 30 formed at each end. Thesecollars provide anchorage arrangements for running wheels 32 and 34which extend around the mold 26 at each end thereof.

The wheels 32 and 34 are dimensioned so that the central axis of theshell 26 remains horizontal while the mold rotates. Thus, it will beseen that the wheel 32 has a shorter web 32a while the wheel 34 has alonger web 340.

Lower and upper end plate members 36 and 38 are fitted into the collars28 and 30 at the opposite ends of the shell 26 respectively. The endplate members 36 and 38 are provided with end walls 40 and 42,respectively, having central openings 44 and 46.

In order to form a concrete pole by means of the device shown in FIG. 4wet concrete, shown at 48, is poured inside the shell 26 and the shellis thereupon caused to rotate rapidly about its longitudinal axis. As aresult of the centrifugal forces produced by such rotation the wetconcrete 48 distributes itself evenly about the inner surfaces of theshell 26. Any excess concrete will find its way out from the endopenings 44 and 46. Thus, as illustrated in FIG. 4, the wet concrete 48which remains within the mold 26 assumes the shape of the finished pole20. The mold 26 continues in rotation until the concrete 48 has fullyformed in this desired finished shape. Thereafter, the mold 26 isstopped and the concrete pole is withdrawn after hardening.

Turning now to FIG. 5 it will be seen that the wheels 32 and 34 eachride upon a driver wheel 50 and an idler wheel 52 which serve to ensurethat the longitudinal axis of the mold 26 remains stationary duringrotation. As shown in FIG. 4, the reinforcing rods 24 may be afflxed bymeans of anchors 54 into the lower end wall 40 before or after theconcrete 48 is poured into the molds. The shorter rods 24 whichterminate at the upper end of the lowermost section A are terminated atfirst intermediate anchors 59. To this end these rods are each caused tobend about an associated anchor plate so that they protrude out throughthe side of the shell 26. The ends of these rods are held in place bymeans of anchor elements 62 mounted on the outer surface of the shell26. As can be seen in FIGS. 4 and 6 there are provided longitudinalslots 64 in the side of the mold 26 at the upper end of the lower regionA where the rods 24 terminate. A pair of outwardly protruding flangeelements 66 are secured to the outer surface of the mold 26, and arepositioned to lie along the opposite sides of each of the slots 64.

The anchor plates 60 are of generally triangular or quarter-roundconfiguration and they extend through the slots 64 down into theinterior of the shell 26. As shown in FIG. 6 the edge of each plate 60is formed with a groove or recess 68 to hold one of the cables 24'securely while the cable passes around the edge of the plate 60 and outthrough the slot 64 to one of the anchor members 62. The plate 60 itselfis secured in place by means of pins '70 which pass through the flanges66 and the plate 60. The rods 24 can be pretensioned to any desireddegree by adjustment of either the anchor member 54 at the lower endthereof or the anchor arrangement 62 at the upper end thereof.

Second intermediate cable termination arrangements 72 are provided atthe upper end of the intermediate section B for terminating the rods 24at the end of this section. The remaining rods 24, which extend the fulllength of the pole 20 through sections A, B and C are terminated inconventional fashion by means of anchors 74 arranged in the upper endwall 42.

After the various reinforcing rods 24 have been properly pretensionedand the assembly has been rotated until the concrete has formed, themold 26 is stopped and subsequently the first and second intermediateanchor arrangements 59 and 72 are removed. This is achieved by releasingthe upper anchors 62 and withdrawing the pins from the anchor plates 60.Thereafter, the anchor plates are withdrawn out from the longitudinalslots 64 and the reinforcing rods 24 and 24" are severed as illustratedin FIG. 7 at locations 76 within the regions 78 voided by the anchorplates 60. The regions 78 are thereupon filled with additional concreteto provide a smooth even exterior for the pole 20. After the variousintermediate anchor arrangements have thus been removed, the end anchorarrangement 54 and 74 are removed as are the end plates 36 and 38. Thefinished pole 20 is then removed from the outer shell 26.

FIGS. 8 and 9 show a modified version of the intermediate anchorassemblies 59 and 72 used in terminating the various cables 24 and 24"..As shown in FIG. 8, the shell 26 is provided at each anchor point with alongitudinal slot 64 and associated side flanges 66. A modified anchorplate 80 of similar configuration to the anchor plate 60 of FIG. 6 isinserted into the slot 64 and is pinned in place as in the preceedingarrangement. In the arrangement of FIGS. 8 and 9 however, the plate isreversedf That is, the curved or slanted edge of the plate which facedrearwardly in the preceeding arrangement, faces forwardly in the presentarrangement. Additionally, in the present arrangement the reinforcingrod 24' loops around a holding plate 82 which abuts a straight sided,non-slanting rearwardly facing surface 84 of the anchor plate 80. Inthis arrangement the pretension on the cable 24 or 24 must be providedby the anchor member 54 at the end of the mold arrangement for there isno adjustable anchor element provided in the intermediate anchor region.

A further intermediate anchor arrangement is shown in FIGS. 10 and 11.Here again the mold 26 is provided with a longitudinally extending slot64 surrounded on both sides by means of longitudinally extending flanges66 which are welded or otherwise secured to the outer surface of themold 26. A further anchor plate 86 extends down into the slot 26 and issecured in place by means of the pins '70 which pass through the plate86 and through the flanges 66. As shown in FIG. 11 the plates 86 areprovided with a fork-like lower end 88 which straddles the reinforcingcable 24. An anchor member 90, similar to the anchor members 54, 62 and74, is provided to abut against a rearwardly facing surface 92 of theanchor plate 86 and to secure the end of the cable 24 in place untilafter the concrete within the shell 26 is fully hardened.

It will be noted that with the two anchor plate modifications shown inFIGS. 8-11 the reinforcing cables 24' and 24 are fully terminated withinthe shell 26 prior to the pouring of the concrete into the shell.Accordingly, it is not necessary when using these two modifications toburn or otherwise sever the reinforcing cables after the concrete hasset.

It will be additionally noted that in all three of the anchorarrangements described there is provided a simple abutting relationshipbetween the reinforcing cables 24' and 24" and the anchor plates 60, 80and 86, so that the anchor plates may readily be removed from the slot64 while leaving the reinforcing cable embedded properly in place.

Those skilled in the art will readily appreciate that while thereinforcing rods or cables shown in the illustrative embodiments onlyhave one end terminated intermediate the ends of the finished structure,any or all of the rods or cables may also have their opposite endsterminated intermediate the ends of the structure. Thus, for example,where the structure is to be driven part-way into the ground and will besubjected to lateral bending loads, the structure may be provided withadditional reinforcement only in the vicinity of the ground level tocounteract the large bending movements which exist in that region. Thismay be accomplished according to the present invention, by providingadditional tensioned reinforcing rods or cables which are terminated atboth ends just beyond the ground line and intermediate the ends of theoverall structure.

Having thus described my invention withparticular reference to thepreferred forms thereof, it will be obvious to those skilled in the artto which the invention pertains, after understanding my invention, thatvarious changes and modifications may be made therein without departingfrom the spirit and scope of my invention, as defined by the claimsappended thereto.

What is claimed as new and desired to be secured by Letters Patent is:

1. An anchor plate arrangement for mounting reinforcing rods insideconcrete molds, said anchor plate arrangement comprising an anchorplate, an anchor plate mounting means adapted for detachably mountingsaid plate to a lateral mold wall to protrude inwardly from said walland means for frictionally abutting said plate to releasably connect areinforcing rod to said plate in a manner permitting said plate tomaintain tension in said rod while permitting ready withdrawal of saidplate from said rod by sliding movement of said plate out from said moldwall.

2. An anchoring arrangement for mounting reinforcing rods insideconcrete molds comprising in combination, an anchor plate, means adaptedfor detachably mounting said plate to a lateral mold wall extendingsubstantially parallel to the longitudinal axis of a reinforcing rodinside said mold, said plate adapted to protrude inwardly from said wallinto said mold and to be slidably removable through said wall, an anchormember adapted to be associatedwith said rod for abutting said anchorplate in a manner permitting said plate to maintain tension in said rodwhile permitting ready withdrawal of said plate from said rod bymovement of said plate out from said mold wall.

3. An anchoring arrangement according to claim 3 wherein said anchorplate has a generally arcuate edge to be engageable with saidreinforcing rod.

4. An anchoring arrangement according to claim 2 wherein said anchorplate is adapted to be held against saidmold wall by pin means.

5. An anchoring arrangement for mounting reinforcing rods insideconcrete molds comprising in combination, a thin plate-shaped anchorplate, means adapted for detachably mounting said plate to a lateralmold wall extending substantially parallel to the longitudinal axis of areinforcing rod inside said mold, said plate adapted to protrudeinwardly from said wall into said mold and having a grooved edge adaptedfor receiving said reinforcing rod and arcuately guiding said rod frominside said mold wall outwardly of said mold wall, and an anchor elementadapted to be mounted outwardly of said mold wall for maintainingtension in said rod.

6. An anchoring arrangement for mounting reinforcing rods insideconcrete molds comprising in combination, a thin plate-shaped anchorplate, means adapted for detachably mounting said plate to a lateral.mold wall extending substantially parallel to the longitudinal axis ofsaid reinforcing rods inside said mold, said plate adapted to protrudeinwardly from said wall into said mold, a holding plate mounted to abutsaid anchor plate adapted for receiving a looped end portion of a pairof said reinforcing rods in a manner permitting said plate to maintaintension in said rod while permitting ready withdrawal of said plate fromsaid rod by movement of said plate out from said mold wall.

7. An anchoring arrangement for mounting reinforcing rods insideconcrete molds comprising in combina: tion, a thin plate-shaped anchorplate, means adapted for detachably mounting said plate to a lateralmold wall extending substantially parallel to the longitudinal axis of areinforcing rod inside said mold, said plate adapted to protrudeinwardly from said wall into said mold and having a grooved edge adaptedfor receiving said reinforcing rod, an anchor member adapted to bemounted on said rod for abutting'said anchor plate for maintainingtension in said rod.

1. An anchor plate arrangement for mounting reinforcing rods insideconcrete molds, said anchor plate arrangement comprising an anchorplate, an anchor plate mounting means adapted for detachably mountingsaid plate to a lateral mold wall to protrude inwardly from said walland means for fricTionally abutting said plate to releasably connect areinforcing rod to said plate in a manner permitting said plate tomaintain tension in said rod while permitting ready withdrawal of saidplate from said rod by sliding movement of said plate out from said moldwall.
 2. An anchoring arrangement for mounting reinforcing rods insideconcrete molds comprising in combination, an anchor plate, means adaptedfor detachably mounting said plate to a lateral mold wall extendingsubstantially parallel to the longitudinal axis of a reinforcing rodinside said mold, said plate adapted to protrude inwardly from said wallinto said mold and to be slidably removable through said wall, an anchormember adapted to be associated with said rod for abutting said anchorplate in a manner permitting said plate to maintain tension in said rodwhile permitting ready withdrawal of said plate from said rod bymovement of said plate out from said mold wall.
 3. An anchoringarrangement according to claim 3 wherein said anchor plate has agenerally arcuate edge to be engageable with said reinforcing rod.
 4. Ananchoring arrangement according to claim 2 wherein said anchor plate isadapted to be held against said mold wall by pin means.
 5. An anchoringarrangement for mounting reinforcing rods inside concrete moldscomprising in combination, a thin plate-shaped anchor plate, meansadapted for detachably mounting said plate to a lateral mold wallextending substantially parallel to the longitudinal axis of areinforcing rod inside said mold, said plate adapted to protrudeinwardly from said wall into said mold and having a grooved edge adaptedfor receiving said reinforcing rod and arcuately guiding said rod frominside said mold wall outwardly of said mold wall, and an anchor elementadapted to be mounted outwardly of said mold wall for maintainingtension in said rod.
 6. An anchoring arrangement for mountingreinforcing rods inside concrete molds comprising in combination, a thinplate-shaped anchor plate, means adapted for detachably mounting saidplate to a lateral mold wall extending substantially parallel to thelongitudinal axis of said reinforcing rods inside said mold, said plateadapted to protrude inwardly from said wall into said mold, a holdingplate mounted to abut said anchor plate adapted for receiving a loopedend portion of a pair of said reinforcing rods in a manner permittingsaid plate to maintain tension in said rod while permitting readywithdrawal of said plate from said rod by movement of said plate outfrom said mold wall.
 7. An anchoring arrangement for mountingreinforcing rods inside concrete molds comprising in combination, a thinplate-shaped anchor plate, means adapted for detachably mounting saidplate to a lateral mold wall extending substantially parallel to thelongitudinal axis of a reinforcing rod inside said mold, said plateadapted to protrude inwardly from said wall into said mold and having agrooved edge adapted for receiving said reinforcing rod, an anchormember adapted to be mounted on said rod for abutting said anchor platefor maintaining tension in said rod.